Basically, VT represents the intensity at which your breathing rate starts to increase in a non-linear fashion. This is often accompanied by a rise in your blood lactate. RCT meanwhile (sometimes referred to as ‘VT2′) represents the (higher) intensity at which your ventilation rate increases further and lactate begins to steadily accumulate.

In a nutshell, you can sustain your cycling training intensity at VT but at RCT, the increasing accumulation of lactate will, at some point, force you to slow down or stop.

Knowing these thresholds can be very useful for tailoring your work intensity. The problem however is that accurate testing to determine these thresholds is time consuming and expensive, involving trips to the laboratory. Moreover, thresholds can easily change as your fitness increases or declines.

But now new research by Spanish and US scientists suggests that there’s a much simpler, cheaper and faster way to reliably determine these thresholds.

The scienceIn the study, eighteen highly-trained cyclists underwent two incremental tests. One test included lab measurements of respiratory gas exchange to determinate the ventilatory (VT) and respiratory compensation (RCT) thresholds. On a separate day, a ‘talk test’ was performed using the same exercise protocol. During talk test, the subjects read a standard paragraph at the end of each incremental stage of the multi-stage test.

The first stage at which each cyclist could not talk comfortably was noted by the researchers (TT1). The next stage of exercise intensity that the researchers noted was when the cyclists could definitely not talk at all (TT2). The scientists then analysed the data to see if and how the cyclists’ VT and RCT were related to TT1 and TT2.

In a nutshellThe key finding was that TT1 and TT2 were very closely related to VT and RCT respectively. In fact, there were no significant differences in workload, heart rate, lactate and rating of perceived exertion between VT and TT1. The same close relationship was also observed between RCT and TT2.

In plain English, at the exercise intensity of TT1, each cyclist’s blood lactate, heart rate and power output was the same as when they exercised at VT and the same relationship was true for TT2 and RCP.

So what?This study shows that in highly trained cyclists at least, it’s possible to get an accurate handle on VT and RCT by using a simple talk test during training. And given that the same physiological principles apply, there’s no reason to think that this method can’t be applied to cyclists of more modest ability too.

Another benefit of course is that since the use of TT1 and TT2 are accurately correlated to blood lactate, this test could be a convenient method of monitoring fitness changes over time – eg to see at what heart rate you reach your TT1 or TT2 (the lower the heart rate, the more efficiently your body is coping with lactate – a strong predictor of cycling performance).

J Strength Cond Res. 2012 Sep 21. [Epub ahead of print]

This article was first published in the November 1 issue of Cycling Weekly. You can also read our magazines on Zinio and download from the Apple store.